Disk drive employing a modified rotational position optimization algorithm to account for external vibrations

Abstract

A disk drive is disclosed which executes a rotational position optimization (RPO) algorithm to select a next command to execute from a command queue relative to an estimated access time. If an external vibration is detected, the RPO algorithm increases at least one of an estimated seek latency, an estimated settle latency, and an estimated rotational latency for each command in the command queue.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to disk drives for computer systems. More particularly, the present invention relates to a disk drive employing a modified rotational position optimization (RPO) algorithm to account for external vibrations.[0003]2. Description of the Prior Art[0004]Rotational position optimization (RPO) algorithms improve the access performance of disk drives by minimizing the seek and settle latency of the head and the rotational latency of the disk. This is illustrated in FIG. 1 which shows a disk drive executing a current command with two commands (COMMAND 1 and COMMAND 2) staged in a command queue. While executing the current command the disk drive will execute an RPO algorithm to select the next command from the command queue having the least access time. In the example of FIG. 1, the disk drive calculates the seek, settle, and rotational latencies in terms of the number of servo wedges and selects th...

AI Technical Summary

Benefits of technology

[0011]In one embodiment, the estimated access time is computed from a reference position on the disk to a beginning of each command in the command queue, wherein the reference position is adjusted by an offset if the external vibration is detected. In one embodiment, the estimated access time comprises an estimated seek latency value and an estimated rotational latency value, the estimated rotational latency value includes the estimated settle latency, and adjusting the reference position by the offset increases the estimated settle latency.

[0014]In another embodiment, the RPO algorithm increases the estimated rotational latency if the external vibration is detected. In one embodiment, the RPO algorithm increases the estimated rotational latency by a partial revolution of the disk for at least one command in the command queue if the external vibration is detected.

Problems solved by technology

However, these estimated settle latencies may be unreliable if the disk drive is subject to an external vibration during normal operation, such as another mechanical device perturbing the disk drive, which can propagate through to the actuator arm and increase the actual settle latency.

In either case the performance degrades since the RPO algorithm does not initially select the optimal command to execute due to the external vibration increasing the actual settle latency.

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